Method for the control of plant growth



United States Patent 3,338,701 METHOD FOR THE CONTROL OF PLANT GROWTHEdward D. Weil, Lewiston, N.Y., assignor to Hooker Chemical Corporation,Niagara Falls, N.Y., a corporation of New York No Drawing. Continuationof application Ser. No.

413,239, Nov. 23, 1964. This application Sept. 6,

1966, Ser. No. 577,533

14 Claims. (Cl. 71--71) This application is a continuation ofapplication Ser. No. 413,289, filed Nov. 23, 1964, now abandoned, whichis a continuation-in-part of Ser. No. 25,842 filed May 2, 1960 by EdwardD. Weil and issued as US. Patent 3,158,461 on Nov. 24, 1964.

This invention relates to the control of plant growth, and moreparticularly, of weeds, by application thereto of a compositioncomprising cycloalkyl or cycloalkenyl phosphine oxides or sulfides.

It has now been found that cycloalkyl and cycloalkenyl phosphine oxidesand sulfides of the formula wherein R, R and R" are monovalent aliphaticradicals, each of which has one carbon atom linked directly tophosphorous and at least one of which is cycloalkyl or cycloalkenyl, andwhere X is oxygen or sulfur, are effective herbicides. They areeffective against both monocotyledonous and dicotyledonous specieswhether applied before or after weed emergence. Such activity issurprising because the phosphine oxides and sulfides are known to beunusually chemically stable and unreactive. They are lacking in labileP-O-C, PNC and P-halogen linkages which are present in various otherknown phosphorouscontaining pesticides. The aliphatic radicals may besimple alkyl radicals or may contain olefinic unsaturation. They may besubstituted by a member of the group consisting of halogen, amino,substituted amino, hydroxy, alkoxy and carboxy. The correspondingphosphines or phosphine-CS addition compounds may be employed, allowingthe reaction mixture to be exposed to air, which readily convertsphosphines to substituted phosphine oxides. The preferred embodiments ofthe invention, for reasons of high activity and relatively low costs,are compounds wherein R, R and R" are alkyl, cycloalkyl or cycloalkenylgroups of four to eight carbon atoms. Various phosphorous compoundshaving halogen, amino, nitrogen, alkoxy or alkylmercapto radicals bounddirectly to the phosphorus atom are sometimes, in some nomenclaturesystems, designated as phosphorous-substituted phosphines, phosphineoxides or phosphine sulfides but such derivatives are reallyphosphinous, phosphonous, phosphinic or phosphonic acid derivatives anduse thereof does not lie within the scope of this invention. The termsphosphine, phosphine oxides and phosphine sulfides, as employed herein,refer to compounds wherein three of the valences of the phosphorus atomare linked directly to carbon atoms. These terms are employed in thismanner by Kosolapoif in Organic Phosphorus Compounds at pages 99-120.

Suitable compounds of a preferred group for use in the method of theinvention include the following oxides and sulfides: tricyclopentyl-;di-n-propylcyclopentyl-; diisopropylcyclopentyl-; dibutylcyclopentyh;dipentylcyclopentyl-; dihexylcyclopentyl-; diheptylcyclopentyl-;dioctylcyclopenty1-; cyclopentyl di-n-propyl-; cyclopentyldiisopropyl-gcyclopentyldibutyl-; cyclopentyldipentyl-; cyclopentyldihexyl-;cyclopentyldiheptyl-; cyclopentyldioctyl-; tricyclopentenyl-;dieyclopentenylbutyl-; dicyclopentylhexyl-; (cyclohexylmethyl)dibutyl-;tris (cyclohexylmethyl)-; (cyclohexylmethyl) pentyl-; tricyclohexyl-;di-npropylcyclohexyl-; diisopropylcyclohexyl-; dibutylcyclohexyl-;dipentylcyclohexyl-; dihexylcyclohexyl-; diheptylcyclohexyl-;dioctylcyclohexyl-; cyclohexyldi-n-propyl-; cyclohexyldiisopropyl-;cyclohexyldibutyl-; cyclohexyldipentyl-; cyclohexyldihexyl-;cyclohexyldihep-tyl-; cyclohexyldioctyl-; tricyclohexenyl-;dicyclohexenylbutyl-; dicyclohexenylhexyl-; tris(4methylcyclohexylmethyl)-; cyclohexenyldicrotonyl-; tricycloheptyl-;tricyclooctyl-; din-butylcycloheptyl-; di-n-butylcyclooctyl-;dipentylcycloheptyl; dipentylcyclooctyl-; dihexylcycloheptyl-;dihexylcyclooctyl-; cycloheptyldipropyl-; cyclooctyldipropyl-;cycloheptyldibutyl-; cycloocty1dibutyl-; cycloheptyldipentyl-;cyclooctyldipentyl-; cycloheptyldihexyl-; cycloheptyldioctyl-;tricycloheptenyl-; tricyclooctenyl-; tricyclobutyl-; and(7-octenyl)dicyclopentyl-.

These compounds, as previously stated, may contain a halogen, amino,substituted amino (preferably alkylamino or dialkylamino), hydroxyalkoxy or carboxy group. Thus, for example, phosphine oxides or sulfidesof the following radicals are useful in the practice of the presentinvention: tris(dichlorocyclohexyl)-; tris(dibromocyclopentyl-;tris(1-an1inocyclohexyl)-; tris 1 (dimethylamino) cyclohexyl)-;tris(l(ethylamino)cyclopentyl)-; tris(lcarboxycyclopentyl)-;tris(2-hydroxycyclooctenyl)-; and similar substituted compounds.

Also useful but less preferred because of lower activities are oxidesand sulfides of: tricyclopropyl-; cyclooctyldimethyl-;cyclohexyldiethyl-; cyclopentyldipr0pyl-; methyldicyclohexyl-;ethyldicyclohexyl-; isopropyldicyclohexyl-; diallylcyclohexyl-;allylbutylcyclohexyl-; (l-diethylaminol-cyclohexyl) dimethyl-; (1carboxy 1 cyclohexyl)- diethyl-; 2-aminoethyldicyclohexyl-;l-methylaminomethyldicyclohexy1-; 2-hydroxyethyldicyclopentyl-; and 2-chloroethyldicyclooctyl.

Thus, the broader scope of the present invention encompasses thephosphine oxides and sulfides having lower (eight or fewer carbon atoms)cycloalkyl, cycloalkenyl, alkenyl or alkyl radicals and having at leastone such cycloalkyl or cyclo alkenyl radical, and the preferred groupwithin this broader group are those compounds wherein each of theradicals possesses from four to eight carbon atoms.

A further preferred sub-group, especially from the standpoint ofmanufacturing ease and herbicidal effectiveness are the phosphine oxidesin which R, R and R" are the same. Similarly, such sulfides are alsopreferred. Examples of such compounds include tricyclobutyl-,tricyclopentyl-, tricyclohexyl-, tricycloheptyl-, tricyclooctyl-,tricycylopentenyl-, tricyclohexenyl-, tricycloheptenyl-, andtricyclooctenyl phosphine oxides and sulfides.

The compounds used in this invention may be prepared by methods known inthe art, such as by the reaction of the corresponding cycloalkyl orcycloanlkenyl Grignard reagent with phosphorus oxychloride,thiophosphoryl chloride or by oxidation of the corresponding phosphineby air or nitric acid or by sulfurization of the corresponding phosphineby sulfur. These methods are described in the Kosolapofi reference citedabove.

Further production methods of such compounds include substitutions onthe alkyl or alkenyl groups of the phosphine oxides or sulfides afterthe unsubstituted compounds have been prepared. For example,tricyclohexyl phosphine oxide may be chlorinated with elemental chlorineat sixty-five degrees centigrade under illumination by a two hundred andfifty watt mercury vapor lamp until the desired weight of chlorine hasbeen taken up, to prepare the mono-, di-, trior higher chlorinatedtricyclohexyl phosphine oxides. Such halogenated cycloalkyl phosphineoxides may be further reacted with amines,

sodium cyanide, sodium alkoxide or other nucleophilic reagent to effectfurther replacement of the halogens.

The methods of the invention may be practiced by application of the purecompounds or formulations comprisother leafy cover, without destructionof the trees and plants, in areas wherein it is desirable to maintainvisibility unobscured by plant growth, such as areas where roads or pipelines are being installed, areas troubled by briging such compounds tothe medium to be treated, the soil 5 andage where the civil or militaryauthorities want to or the plant, the growth of which is to becontrolled or maintain good visibility of personnel in the area, and soprevented. Formulations may be solutions of the comforth. The killing ofpotato vines aids in the harvesting pounds or mixtures thereof insolvents such as water, of potatoes. acetone, ethanol, other alcohols,hydrocarbons, such as The following examples illustrate the invention.They benzene, kerosene, diesel oil, crude oil, xylene or other are notlimiting thereof. All parts are by weight and temaromatic or aliphatichydrocarbon. Solutions in organic peratures are in degrees Centigradeunless otherwise insolvent may be further dispersed in water asemulsions, dicated. with the aid of emulsifiers known to the herbicideart. Example 1 The may also comPnse the acuve mammal A representativeherbicidal composition of the invenon an inert carrier, usually a solid,such as clay, carbon tion is the fouowing. or a vermiculite, with orwithout wetting or dispersing Parts agents. Such formulations may alsoinclude other herb1 Tricyclohexyl phosphine Oxide 10 cides tosupplement, complement, synergize or enhance Xylene (Solvent) 10 theherbicidal activity of the active compounds employed Aflox 3335(polyoxyethylene emulsifier) 2 111 this invention. Since the presentcompounds are generany fast acting, they may be employed together withThis mixture is emulsified with water in any convenient slower actingherbicides, such as triazine herbicides, aryl P P for p y alkyl ureaherbicides, 2,4-D, 2,4,5-T, aminotrichloropic- Example 2 clinic acid or2,3,6-trichlorophenylacetic acid herbicides. The formulations may alsoinclude solubilizers for the A ffipresentatlve formulation of thematerial active materials For example the phosphine Oxides may useful inthe process of the invention is the following: be solubilized by eitherhydrochloric acid or other acid Part in aqueous solution. The mentionedformulations may Tricyclopentenyl phosphine oxide 1 also contain otheradjuvants, such as sequestering agents, Diesel oil 1O colorants,wetting, spreading and sticking agents, in accordance with knownpractices in the herbicide art. ,Thls m 1Xtur e y be sprayed as 15 ormay be further The methods of employing the mentioned compositions(muted Wlth dlesel 011 or keroseneinclude applying them to the soilprior to the emergence Example 3 of weeds. They may be mixed with thesoil, if desired, to aid penetration. They may also be applied to thefoliage A series of representative plant species was selected for of theemerged weeds and other plants. The application evaluation of theherbicidal method of the invention. to the foliage may be made for thepurpose of defoliation Greenhouse flats were seeded with beans,cucumbers, or desiccation of the foliage or for the purpose ofstunttomatoes, cabbage, millet, crabgrass and ryegrass, coning thegrowth of the plant to which applied, as well as sidered to berepresentative of types of plant growth and for the purpose ofcompletely destroying the plant. For normally used in standardherbicidal testing. In preexample, the compounds and compositionsthereof, when emergence tests, the chemical was applied in aqueoussprayed onto corn foliage, killed the foliage without indispersion priorto emergence of the seedlings. In postjury to the ears, resulting in amore rapid drying of the emergence tests the chemical was applied to theseedlings ears, which is often desirable, since dried corn can be abouttwo weeks after emergence. The resultant control stored with lessdeterioration than wet corn. The stunting of plant growth was determinedabout one week after of trees without causing the deaths thereof isuseful to application of the chemical. The observed results were asinhibit excessive growths of trees under electric power follows:

Post-Emergence (Rate of 4 pounds/acre) Chemical Applied Beans Cue. Tom.Cab. Millet Crabgrass Ryegrass Trioyclopentylphosphiiie oxide 8 5 8 5 55 5 Tricyclohcxylphosphine oxide 10 10 9 4 5 4 0Cyclohexyldi-n-hcxylphosphine oxide 9 9 8 9 5 9 10 Pro-Emergence (Rateof 8 pounds/acre) Tricyclopentylphosphine oxide 7 5 9 6 7 6 7 Scale: 0=n0 effect; 1-3 slight control; 4-6 =moderate control; 7-9 =strongcontrol; 10 complete kill. Abbreviations: Cuc. =cucumbers; Tom.=tomatoes; Cab. =cabbages.

and telephone lines, with which they might otherwise interfere. Thedesiccation of cotton foliage, without killing of the plants aids in theharvesting of the bolls and in their being obtained free of excessiveamounts of color ing materials and leaf fragments. The rapid generalkilling of foliage is also useful in removing tree,

In addition to the above data, it is noted that tricyclohexylphosphineoxide exerts a strong controlling effect against crabgrass when appliedat the rate of 8 pounds/ acre in pre-emergent treatments. When thesulfides are employed in place of the oxides, good results such as thosebrush and given above are also obtained.

Example 4 Scale" =no effect; l3=slight desiccation; 46=moderatedesiccation; 79=severe desiccation; 10=c0mpleteifoliar kill.

Example The effects of various comparison materials andtricyclohexylphosphine oxide were compared. It was found that thecompound employed by the method of this invention was significantly moreeflective against both grasses and broadleaf weeds, as shown in thefollowing table.

An area infested with well-established perennial grasses, mostlyquackgrass, and perennial broadleaf weeds, mostly plantain, wild carrot,and goldenrod, was divided into plots and sprayed with diesel oilformulations, similar to those of Example 2, at the rate of eightygallons of oil per acre containing four pounds per acre of the testherbicide. Comparison plots were also sprayed using eighty gallons peracre and higher rates of the oil alone. The results, in terms ofseverity of top kill (foliar destruction) were observed three days laterand are tabulated below:

The present invnetion has been described with respect to examples, givenfor illustration, not limitation. Many other modifications andsubstitutions of equivalents will naturally suggest themselves to thoseskilled in the art, based on the present disclosure, and are within theinvention.

What is claimed is:

1. A method for the control of plant growth which comprises applying tothe medium to be treated a growth 'controllin-g amount of a compositionof the formula wherein R, R and R" are monovalent radicals selected fromthe group consisting of lower cycloalkyl, lower cycloalkenyl, loweralkyl, lower alkenyl, lower haloalkyl, lower aminoalkyl, lower.alkylaminoalkyl, lower dialkylaminoalkyl, lower hydroxalkyl and lowercarboxyalkyl, wherein R, R and R each have one carbon atom linkeddirectly to the phosphorus atom, and at least two of these radicals areselected from the group consisting of lower cycloalkyl and lowercycloalkenyl, and X is selected from the group consisting of oxygen andsulfur.

2. The method of claim 1 wherein R, R and R" are each lower cycloalkylof from 4 to 8 carbon atoms.

3. The method of claim 1 wherein at least one of the monovalentradicals, R, R and R", is lower cycloalkyl of 4 to 8 carbon atoms.

4. The method of claim 1 wherein at least one of the monovalentradicals, R, R and R, is lower cycloalkyl.

5. The method of claim 1 wherein at least one of the monovalentradicals, R, R and R, is lower cycloalkenyl.

6. The method of claim 1 wherein at least one of the monovalentradicals, R, R and R", is lower carboxycycloalkyl.

7. The method of claim 1 wherein at least one of the monovalentradicals, R, R and R, is di-lower-alkylaminocyclo-lower-alkyl.

8. The method of claim 2 wherein R, R and -R are the same.

9. The method of claim 8 wherein R, R and R are each cyclopentyl and Xis oxygen.

10. The method of claim 8 wherein R, R and R are each cyclohexyl and Xis oxygen. 7

11. The method of claim 1 wherein a herbicidally effective amount of isapplied.

12. The method of claim 11 wherein R, R and R" are each lower cycloalkylof from 4 to 8 carbon atoms.

13. The method of claim 12 wherein R, R and R are each cyclopentyl and Xis oxygen.

14. The method of claim 12 wherein R, R and R are each cyclohexyl and Xis oxygen.

References Cited UNITED STATES PATENTS 2,714,064 7/ 1955 Morris et 'al712.7 X 2,844,454 7/1958 Birum 712.7 2,927,014 3/1960 Goyette 712.33,104,259 9/1963 Harwood et a1 71-23 3,158,461 11/1964 Weil 712.7

OTHER REFERENCES Plant Regulators, National Academy of Sciences,National Research Council, Publication 384, CBCC Positive Data SeriesNo. 2, June 1955, pp. A, B, C, 1 and 38.

LEWIS GOTTS, Primary Examiner. J. O. THOMAS, 111., Assistant Examiner.

1. A METHOD FOR THE CONTROL OF PLANT GROWTH WHICH COMPRISES APPLYING TOTHE MEDIUM TO BE TREATED A GROWTH CONTROLLING AMOUNT OF A COMPOSITION OFTHE FORMULA